# 工廠模式 Factory

一個class當作工廠，會負責回傳出相對樣的其他class。

舉例來說有一個class叫做factory，他的工作是負責生產card，所以我們還要生成各個card的class，當我們使用factory的create方法的時候會回傳一個給card的class給我們。

public abstract class Factory {
//先以 createProduct 製作產品，再以 registerProduct 完成登錄
    public final Product create(String owner) {
        Product p = createProduct(owner);
        registerProduct(p);
        return p;
    }
    protected abstract Product createProduct(String owner);
    protected abstract void registerProduct(Product product);
}

public class IDCardFactory extends Factory {
    private Vector owners = new Vector();
    protected Product createProduct(String owner) {
        return new IDCard(owner);
    }
    protected void registerProduct(Product product) {
        owners.add(((IDCard)product).getOwner());
    }
    public Vector getOwners() {
        return owners;
    }
}
public abstract class Product {
    public abstract void use();
}

public class IDCard extends Product {
    private String owner;
//只能夠在同一個 package 中呼叫建構子
    IDCard(String owner) {
        System.out.println("建立" + owner + "的卡。");
        this.owner = owner;
    }
    public void use () {
        System.out.println("使用" + owner + "的卡。");
    }
    public String getOwner() {
        return owner;
    }
}

public class Main {
    public static void main(String[] args) {
        Factory factory = new IDCardFactory();
        Product card1 = factory.create("結城浩");
        Product card2 = factory.create("戶村");
        Product card3 = factory.create("佐藤花子");
        card1.use();
        card2.use();
        card3.use();
    }
}

> [name=閔致]

# The differences between "Factory Method" and "Simple Factory Method".
## 工廠模式和簡單工廠模式的差別。

Suppose we have these code.

public interface Pizza{
    void print();
}

public class NewYorkPizza implements Pizza{
    public void print(){
    System.out.println("I am NY Pizza");
    }
}

public class ChicagoPizza implements Pizza{
    public void print(){
    System.out.println("I am Chicago Pizza");
    }
}

Here is the code for the Factory Method.

public abstract class PizzaFactory{
    Pizza getInstance();
}

public class NewYorkPizza extends PizzaFactory{
    Pizza getInstance(){
        return new NewYorkPizza();
    }
}

public class ChicagoPizza extends PizzaFactory{
    Pizza getInstance(){
        return new ChicagoPizza();
    }
}

Here is the code for the Simple Factory Method.

public class SimplePizzaFactory{
    public Pizza getInstance(String type){
        switch(type){
            case "NY":
               return new NewYorkPizza();
            case "Chicago":
               return new ChicagoPizza(); 
            default:
               return null;
        }
    }
}

### To sum up, in the Factory Method, each Concrete Factory decides which product would be instantiate. However Simple Factory Method would create the object by the "type" that client passed in.
> [name=YuanChangLee]